JSFiddle - React, Tailwind, and code Playground

HTML

<div id="fadein"></div>
<form>
    <input type="username" placeholder="Username"><br />
    <input type="password" placeholder="Password"><br />
    <div id="button">Sign In</div>
</form>

CSS

* {
    margin: 0px;
    padding: 0px;
}
html {
    background: #777;
    height: 100%;
    width: 100%;
}
form {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 400px;
    height: 124px;
    margin-top: -62px;
    margin-left: -200px;
}
input {
    width: 360px;
    padding: 10px;
    margin: 10px;
    height: 20px;
    border-radius: 50px;
    border: 1px solid #ccc;
    color: #aaa;
    -webkit-transition: all 0.5s linear;
}
input:focus {
    outline: 0px;
    background: #ccc;
    color: #555;
    -webkit-box-shadow: 0px 0px 10px #333;
}
#button {
    background: #b0b2b3;
    border: 0px;
    border-radius: 4px;
    width: 70px;
    height: 30px;
    color: white;
    font-size: 14px;
    font-family: Arial, Veranda, sans-serif;
    line-height: 30px;
    text-align: center;
    text-transform: uppercase;
    margin-left: 310px;
}
#button:hover {
    cursor: pointer;
    background: #a2a2a3;
}
#fadein {
    position: absolute;
    background: black;
    opacity: 0;
    width: 100%;
    height: 100%;
    -webkit-animation: fadein 2s 1 linear;
}
@-webkit-keyframes fadein {
    0% { opacity: 1; z-index: 2;}
    99%{ z-index: 2;}
    100% { opacity: 0; z-index: 0;}
}